305 Scrambler motor right cylinder popping

[moondoggers]

A new issue has come up after using the LM method tune-up the right cylinder is popping.
The motor runs strong through all gears. I have finally gotten the motor to run well and I am having fun riding the bike .
Could this be a valve not seating?

[Tango911]

could be that yes. check the compression on both cylinders.

[mike in idaho]

More likely the slide is lower on the side doing the popping. Time to balance the carb settings again.

[moondoggers]

Looks like I'll need to have the top end rebuilt, I did a compression check on both sides with the right at 70 lb and left at 120 lb.
I'm out here in north central Arizona in the Chino Valley area, is anyone out there close that would do the work.
I will pull the motor.

[moondoggers]

While building a set of work benches today a couple things came to my pea sized brain that might cause the low compression, the first thought was valves out of adjustment and second maybe carbon deposits on the valve seat.
There was an oil leak issue with the right cylinder last June that may tie in with the compression.
Tomorrow I adjust the valves.
Will Marvel Mystery Oil harm the the clutch, gaskets or rubber O rings if I use a little in the crankcase oil and or or gas tank to remove the carbon deposit before I pull the motor?

[hondadreamca77]

I currently use MMO in my 305 oil and fuel (sparingly in fuel) with no adverse affects. In fact, the gears seem to be shifting smoother since adding. Maybe someone else can chime in about seals, etc. being affected by MMO. Used it on my old 750 four for years as well. No problems.

Steve